Greensboro, NC -- Autopsies show a North Carolina woman who killed five children, wounded a former lover and killed herself in November had no drugs in her system, but investigators found a bag containing cocaine.

The state medical examiner's office in Chapel Hill on Tuesday released reports for 36-year-old Mary Ann Holder and her victims. All were shot in the head with a .38-caliber handgun.

Holder's autopsy found only caffeine in her system. A small plastic bag containing cocaine and a chemical used to dilute the drug was in her vehicle.

Guilford County Sheriff BJ Barnes says investigators couldn't find a clear motive for Holder's shooting rampage. In January, Investigators said Holder was the only shooter.

Mary Ann Holder shot to death her 17- and 14-year-old sons, her 8-year-old niece, her 17-year-old nephew, and the 15-year-old girlfriend of her older son.